What is the purpose of Group By in aggregation?

• A. Define a table structure
• B. Group records for summarization using aggregate functions
• C. Compute a derived field
• D. Link two tables

Answer: (B)

Grouping records into subsets that share common values is what Group By enables. It organizes rows into groups so that aggregate calculations can be applied to each group, producing a summary per subgroup instead of a single total for the whole table. For example, you can use Group By to get total sales per region or the average score per class. This is typically paired with aggregate functions like SUM, COUNT, AVG, MIN, and MAX to produce meaningful summaries for each group. Grouping can be done on multiple columns to create more granular subtotals, and you can filter the resulting groups with a HAVING clause if needed. This differs from defining a table’s structure, deriving a new field independently, or joining tables, which are unrelated to the purpose of creating summarized groups.